Valorizing tropical fruit byproducts into a biodegradable, active, and colorimetric film for smart chilled fish packaging solution

Abstract This work reports an experimentally validated, multifunctional, fully biodegradable indicator film made from fruit waste components, blending polyvinyl alcohol (PVA) with pectin isolated from durian rind and betalains from red dragon fruit peel. PVA/pectin films prepared at various blend ratios were characterized (physical, structural, and morphological), and assessed for swelling, solvent resistance, and soil biodegradation (11.6–46.2 % mass loss after 28 days, depending on pectin content). The 75:25 PVA/pectin film showed the best balance of tensile strength and resistance to water/common solvents, and was therefore selected as the matrix for chromogenic films with 0.15% (PPB 0.15%) or 0.20% (PPB 0.20%) betalains. Functional tests demonstrated clear, reversible color transitions over a wide pH range and in the presence of ammonia vapor. Antioxidant activity was benchmarked against Trolox (IC₅₀ = 0.01312 mg mL⁻¹), with the films achieving IC₅₀ values of 4.72 mg mL⁻¹ (PPB 0.15%) and 4.37 mg mL⁻¹ (PPB 0.20%). Antibacterial assays showed inhibition zones against Escherichia coli of approximately 21.0 ± 0.5 mm for PPB 0.20%, exceeding the literature baselines for comparable plant-pigment films (approximately 9.6–13.5 mm, with upper reports of approximately 26 mm). In a real-food validation with chilled mackerel at 4 °C, the PPB 0.20 % film shifted from red to yellow on day 2, coinciding with TVB-N > 25 mg N 100 g⁻¹ (regulatory freshness limit). The PPB 0.20 % film is a promising intelligent/active packaging material, simultaneously delivering freshness indication, antioxidant protection, antibacterial functionality, and biodegradable potential.